SCK + CO2¶

Grade: intermediate

Measure Indoor or Outdoor Air Quality with this unit. Beyond the metrics from the kit, it can measure CO2 with a very reliable CO2 sensor!

Smart Citizen CO2 Air Quality Station

Measurements¶

SCK2.3 basedSCK2.1 based (deprecated)

Measurement	Units	Sensor
Air temperature	ºC	Sensirion SHT-31
Relative Humidity	% REL	Sensirion SHT-31
Noise level	dBA	Invensense ICS-434342
Ambient light	lux	Rohm BH1721FVC
Barometric pressure	kPa	NXP MPL3115A26
Equivalent Carbon Dioxide	ppm	AMS CCS811
Volatile Organic Compounds	ppb	AMS CCS811
Particulate Matter PM1, PM2.5, PM4.0 PM10	µg/m3	Sensirion SEN5X
CO2	ppm	Sensirion SCD30

Measurement	Units	Sensor
Air temperature	ºC	Sensirion SHT-31
Relative Humidity	% REL	Sensirion SHT-31
Noise level	dBA	Invensense ICS-434342
Ambient light	lux	Rohm BH1721FVC
Barometric pressure	kPa	NXP MPL3115A26
Equivalent Carbon Dioxide	ppm	AMS CCS811
Volatile Organic Compounds	ppb	AMS CCS811
PM1, PM2.5 and PM10	µg/m3	Plantower PMS5003
CO2	ppm	Sensirion SCD30

Technical specifications¶

Smart Citizen CO2 Air Quality Station

Dimensions and weight¶

Version	Dimensions	Weight
Indoor	16.6 x 12.5 x 5.5 cm	330g
Outdoor (with umbrella)	23.1 x 14.7 x 8.5 cm	1050g

Design files

If you are looking for the design files about the Smart Citizen Station, take a look at the enclosures repository.

Power¶

Currently, the Smart Citizen Air Quality Stations have only been tested with an external power supply (230VAC to 5VDC), with a small battery for backup during power brownouts. Due to the number of sensors, and depending on the configuration the solution is normally not meant for long term deployment with just battery power. For detailed specifications of the power supply, visit the power supply section.

Power
DC Voltage	5V
DC Current	2A recommended
AC Voltage	230V into the Power Supply
AC Current	<0.16A into the Power Supply

Battery or solar operation?

The Station currently supports battery operation only for short periods of time (<2d days). Depending on the location, solar power might be available, but we do not recommend it unless you are willing to experiment.

Connectivity¶

Similar to the Smart Citizen Kit if you want to have your data online, the Smart Citizen Air Quality Station requires a Wi-Fi connection to report data to the platform. If not, the unit can also store data locally on its onboard sd-card. Read more about the operation modes and the supported networks.

Hardware design¶

A note about versions

Some of the diagrams below are from older designs, but you they haven't changed much! Hopefully they are still understandable!

The Stations should come assembled and ready to use. They consist of various parts:

Enclosure and mounting system: for protection and support.
Sensors module: contains the electronics and sensors, it can be accessed without having to uninstall the rain cover.
Power supply: is separated from the main module, so that intervention in the sensors' area can be performed safely with a tangible desconection of the mains power.

Enclosure and mounting system¶

The enclosure holds the sensors in place and protects them against weather. A rain and sun radiation cover for additional protection can be used, which carries out the structural support of the station and protects the unit against rain, wind or heat.

Flexible attachment

This mounting is thought to work on a lampost, fence or wall. We recommend a somewhat flexible join (i.e. zip-ties) in case of windy locations.

The enclosure can be installed using the mounting holes seen below. There is sufficient space to pass zip ties. If you want to use drills, we recommend at least 6mm screws (or 8mm) and to dissasemble the plastic cover from the sandwich pannel for safer installation.

Deployment tips¶

Below are some general guidelines for the installation of the device:

Avoid areas with moist accumulation when possible
Avoid temperature and humidity transients
Avoid covering the sensors in front of the sensors, specially the PM sensor
Avoid covering the microphone and particles to go in the microphone port
Avoid direct flow towards the sensors. If exposed under flow conditions, have the flow go parallel to the sensors' surface
Despite the umbrella cover, sun radiation and transients are better to be avoided
A good height for installing the sensors is somewhere between 2-3m, but it all depends on the case study and available support structures.

Handling calibration data¶

Some components of the Station have individual calibrations such as the Alphasense Electrochemical Sensors. For this reason, it's necessary to store the physical ID (hardware ID) of the Station alonside to the virtual device in the Smart Citizen Platform. The harwdware ID should normally be in a sticker to the enclosure both inside and outside and looks like this:

SCAS2100XX

This number is important to relate to the actual calibration values of the sensors, stored in the data repository. In order to postprocess the data and calculate pollutants, make sure that the Hardware ID is safely stored in the platform's device, by posting this data to postprocessing_info field of the device. You can follow these instructions to store the postprocessing_info of your device.

All the data is sent in raw to the Smart Citizen Platform and it's then processed outside of the sensors themselves. Both raw, and processed data are kept on the platform and can be accessed at any time. Data can be published to other APIs or to Zenodo as well, in case of research projects that seek contribution to Open Science Datasets.